In contemporary mixed analog-digital signal processing integrated circuits, electrical noise or interference generated by on-chip digital circuits reduces fidelity of analog signals being processed by on-board analog circuits. Circuit architectures for these analog circuits include analog sampled-data or switched-capacitor circuits. In a switched-capacitor circuit, an analog signal can be periodically coupled to a capacitor which is charged by the analog signal. While the analog signal is coupled to the capacitor, transitions of on-chip digital signals which include a signal controlling the aforementioned coupling action, can reduce the fidelity of the coupled analog signal because interference associated with the transitions of on-chip digital signals can be coupled into the analog signal.
In one case, the interference can take the form of power supply perturbations associated with transitions of various on-chip digital signals. This interference can manifest itself in the form of an offset error in the analog signal being processed.
In another case the interference can be somewhat random and associated with certain operations of the mixed-mode circuit hosting the analog circuit. For instance, if a logical operation--such as gating integrated output drivers is functioning while the analog signal is being processed electrical perturbations can infiltrate the analog signal, thereby reducing the analog signal's fidelity.
What is needed is an approach that may include a system and/or method for improving signal fidelity in mixed-mode analog-digital signal processing circuits that is usually degraded dependent on interference attributable to on-chip digital signals.